Preservative-type functional fluids



Patented Jan. 1, 1963 3,071,549 PRESERVATIVE-TYPE FUNCTIONAL FLUIDSLouis R. Stark, East 5t. Louis, 111., assignor to Monsanto ChemicalCompany, St. Louis, Mo., a corporation of Deiaware No Drawin Filed Dec.17, 1959, Ser. No. 850,063 5 Claims. (Cl. 252-78) This invention relatesto fire-resistant functional fluids having outstanding preservative orrust-preventive properties which fluids are composed of the fluidtriaryl phosphates containing an additive amount of a dimer acid.

The manufacturer of hydraulically operated equipment, such as a pump,transmission, die-casting machine, etc., usually provides an initialfill of such equipment with a hydraulic fluid and operates suchequipment for a short period of time on the initial fill to insure thatthe particular item of equipment operates satisfactorily. Additionally,this initial operation contacts the internal parts of the equipment withhydraulic fluid so that after the hydraulic fluid is drained prior toshipment or storage, a film of the hydraulic fluid remains on theinternal parts of the equipment and thereby provides protection of theparts against rusting. Similar action is also taken in situations whereequipment is to be removed from service for an extended period of time,as for example, when a manufacturing facility is closed down or as whenone of the branches of the Armed Services, such as the Navy, moth ballssome of its equipment.

The use of petroleum-based fluids containing suitable anti-rustadditives as storage preservatives is known. With the increasingpopularity of synthetic fire-resistant fluids, however, many problemsare presented when these latter fluids are used to provide storageprotection. The use of petroleum-based fluids as storage preservativesfor equipment designed to eventually operate on a synthetic fluid isundesirable since any remaining petroleum oil could (a) decrease thefire resistance of a later added fire-resistant synthetic fluid, (11)possibly be incompatible with seals installed for use with syntheticfluids, and (c) be incompatible with the synthetic fluids. On the otherhand, most of the synthetic fluids do not inherently possess theproperty of providing protection against rust formation on ferroussurfaces under storage conditions, and normal additive quantities of theanti-rust additives generally used in petroleum-based fluids do not helpin providing the synthetic fluids with adequate rust inhibitionproperties as shown by the fact that synthetic fluids frequently requirevery large quantities (often as much as 20%) of the same additives asare normally used with petroleum based fluids to provide the desiredlevel of rust protection. However, the use of such large quantities ofadditives results in a fluid having an unrealistic cost for mostcommercial applications and also greatly reduces the fire resistance ofthe synthetic fluids. It has now been found that syntheticfire-resistant triaryl phosphate-based fluids can be utilized aspreservative fluids by adding thereto an additive amount of ahereinafter-described dimer acid. The resulting composition providesstorage preservation for a period of time equal to that normallyexpected from petroleum-based fluids even under severe conditions oftemperature and humidity.

It is an object of this invention to provide synthetic fireresistantfunctional fluids having superior preservative or rust-preventiveproperties. It is a further object of this invention to providesynthetic fire-resistant functional fluids which in a fill and draintype operation, as heretofore described, provide anti-rust protectionfor an extended period of time even under conditions of high temperatureand high humidity. These objects will be readily apparent to thoseskilled in the art from the following description of the invention.

It has now been discovered that the fluid triaryl phosphates containingan additive amount, i.e. up to about 10% by weight, of a dimer acid,provide syntheticfireresistant functional fluids having outstandingpreservative or rust-preventive properties. The triaryl phosphatesofthis invention can be represented by the general formula:

O=PO-Rz where R R and R are each selected from phenyl, alkylphenyl,halophenyl, alkylhalophenyl, and haloalkylphenyl radicals. Of thealkyl-substituted phenyl radicals, including those radicals containinghalogen substituents, the methyl-substituted phenyl radicals arepreferred. Within the scope of the invention, various mixtures oftriaryl phosphates can be used, and the substituted phenyl groups withina particular triaryl phosphate need not be the same. Non-limitingexamples of suitable radicals are phenyl, cresyl, xylyl, ethylphenyl,isopropylphenyl, tert.-butylphenyl, amylphenyl, decylphenyl,chorophenyl, naphthyl, trifluormethylphenyl, 2,2,2-trifluorethylphenyl,methylchlorophenyl, diphenyl, and the like.

When two like or unlike molecules of a polyethenoid monocarboxylic fattyacid condense to form a dicarboxylic acid, the product by definition isa dimer acid, or the carboxylic acid is said to be dirneriz/ed. Ingeneral, the dimer acids suitable for use in this invent-ion areproduced by the condensation of two like or unlike unsaturated aliphaticmonocarboxylic acids having between about 16 and about 18 carbon atomsper molecule, examples of which comprise d -hexadecadienoic acid n-heptadecadienoic acid A -octadecadienoic acid A -octadecadienoic a'cidA -octadecadienoic acid (linoleic acid) A -octadecadienoic acid A-octadecatrienoic acid A -octadecatrienoic acid (linoleic acid) Thedimer acids can be characterized as being dicarboxylic' acids havingeither one substituted six-membered hydroaromatic ring or having twofused six-membered hydroaromatic rings, one of which does not carry thetwo carboxylic acid groups being disubstituted. These acids are furthercharacterized by having two carboxylic acid groups attached to a singlesix-membered hydroaromatic ring through a plurality of (GHQ-groups, thenumber of such groups being dependent upon the number of such groupsbetween the carbon atom of the carboxylic acid group and the nearercarbon of the nearest double bond of the monocarboxylic acid. Thesubstituents are .alkyl or alkenyl groups, depending upon the degree ofunsaturation of the monocarboxylic acid from which the dimeric acid isderived. Thus, the dimer acids derived from a diethenoid fatty acid, ora dienoic acid, have a single fsix-membered hydroaromatic ringsubstituted in two immediately adjacent positions by two alkyl groupsand in two other immediately adjacent positions by carboxylic acidgroups separated from the hydroaromatic rin-g in one substituent by astraight-chain unsaturated aliphatic group and in the other by astraight-chain saturated aliphatic group. Consequently, dimer acids,when prepared from the individual monocarboxylic acids, are representedby two formulae; i.e.,

where R is CH (CH and R is -(CH COOH, and n is a small number one morethan the number of CH groups between the terminal CH -group and thenearer carbon of the nearer double bond of the diethenoid monocarboxylicacid from which the dimer acid is derived, and m is a small numberrepresenting the number of CH groups between the carbon of thecarboxylic group and the nearer carbon of the nearer double bond of thediethanoid monocarboxylic acid from which the dimer acid is derived; and

where R" is CH (CH and R' is -(CH COOH, and n and m have the samesignificance as before. Thus, the dimer acids are dicarboxylic acidsderived from two molecules of polyethenoid fatty acids of drying andsemidrying oils and from fatty acids such as ricinoleic acid which, upondehydration, become polyethenoid fatty acids. Therefore, in general,dimer acids are dicarboxylic acids derived by the condensation of twomolecules of one or more polyethenoid aliphatic monocarboxylic acids.

While the dimer acids can be used in pure form, for practical reasons,impure forms are used; that is to say, the dimer acids are not presentlyavailable at commercially attractive costs in pure form. The purest formexamined contained about 85% dimerized acidsthe impurest sample examinedcontained about 45% dimerized acids. The preferred dimer acid for use inthis invention is dimerized linoleic acid which is obtained bycondensing linoleic acid. Linoleic acid may be condensed by heating at atemperature of 330-360 C. in the presence of a small amount of water orin an atmosphere of steam for a period of three to eight hours atpressures varying be tween 85 and 400 pounds per square inch. Theresulting product consists essentially of the dimer, but minorproportions of the trimer are also formed. Methods for carrying out thisprocedure in detail may be found in the article by Charles G. Goebel,Journal of the American Oil Chemists Society, vol. 24, pp. 658 (1947). Awellknown source of this dimerized linoleic acid is the product sold byEmery Industries, Inc., the properties of which are given as follows:

Neutral equivalent 290-310.

Iodine value -95.

Color Gardner 12 (max.). Dimer content Approx. Trimer and higher Approx.12%. Monomer Approx. 3%.

Tests of several batches of material supplied by this producer indicatethat the properties of this product are within the following limits:

Specific gravity, A.P.I l5-15.l Specific gravity, D60/60 0.9665 Color,Lovibond 35 Kinematic viscosity at F., centistokes 2462-2666 A.S.T.M.bromine N0 39.3

Neutrality No 186.8190.4 Iodine value 67-86 It will be noted that thedimer acids available from the Emery Industries, Inc., containapproximately 85% dimerized acids and about 12% trirnerized and higherpolyrneric acids.

Another source of dimer acids is the still residue from the drydistillation of castor oil in the presence of sodium hydroxide. Thisdistillation yields approximately two equal fractions, the distillateand a second still residue, which residue contains about 45-50%dimerized acids and about 50% trimerized and higher polymeric acids.Since neither of these industrially available products are 100%dimerized acids, it is manifest that materials containing more highlypolymerized acids than the dimer acids can be used. However, it is to benoted that these materials contain only small amounts, say less than10%, of the monocarboxylic or unpolymerized fatty acids and saturatedacids. Accordingly, preferred dimer acids are those containing not morethan about 15% of unpolymerized unsaturated fatty acids and saturatedfatty acids.

In general, the content of dimerized acids and trimerized and higheracids should be of the order of at least about 85%, with the dimer acidsrepresenting at least about 50% of the dimeric and higher polymericacids. The Emery Industries dimer acid contains about 85% dimerizedacid, while the second still residue of the dry distillation of castoroil, in the presence of sodium hydroxide contains about 46.8% dimerizedacids.

In order to demonstrate the outstanding rust-preventing properties ofcompositions of this invention, Federal Test Method Standard No. 791,Method 5323-T, was used, by which test the degree of protection providedby mineral or synthetic lubricating oils under conditions of specifiedtemperature and humidity can be determined. Test panels prepared asspecified in this method and dipped in formulations compounded accordingto this invention gave protection against rust for a period of at leastthirty days.

Some typical formulations of this invention which give anti-rustprotection for thirty days in the above described test are as follows:

Dimer acid,

Such results are outstanding when it is considered that using the samemethod test panels coated with triaryl phosphates alone (i.e. withoutthe addition of a dimer acid) showed an average of about 40% rustingafter 24 hours. Amounts of dimer acid as low as about 0.25% providedefinite improvement of the anti-rust properties of the fluid triarylphosphates and are therefore contemplated as part of the invention. Suchsmall amounts do not however provide a minimum of about 30 daysprotection in the above-described rust test. For anti-rust protection ofthe order of 30 days about at least 2% dimer acid should be used.

The physical properties of the formulations of this invention do notdiffer materially from the properties of the triaryl phosphate basestocks. Thus, for example, the physical properties of both a formulationof this invention (tricresyl phosphate plus dimerized linoleic acid) andthe triaryl phosphate base stock (tricresyl phosphate) are compared inthe following table.

PROPERTY Tricresyl Tricresyl Phos- Phosphate phate 5.0% dimer acidViscosity, 100 F Viscosity, 210 F Specific gravity, 60l60 I Flash Point,Cleveland Open Cup. Fire Point, Cleveland Open 32. 6 centistokes. 4. 23centistokes.

Off-White.

43. 7 centistokes.. 5.07 centistokes Tan-Amber Table Viscosity, centi-Specific stokes Gravity, COMPOSITION 60l60 F.

Cresyl diphenyl phosphate 17. 9 3. 29 1. 205 Cresyl diphenyl phosphatedimer acid 23.1 3. 85 1. 200 Dicresyl phenyl phosphate. 24. 6 3. 79Dicresyl phenyl phosphate dimer acid 31.9 4. 50 Diphenyl B-naphthylphosphate 63.4 6.15 1. 242 Diphenyl B-naphthyl phosphate dimer acid 84.17.41 1. 238 Diplienyl a-naphthyl phosphate 64. 7 6. 20 1. 246 Diphenyla-naphthyl phosphate dimer acid 86. 2 7.62 1. 232 Dicresyl a-naphthylphosphate 176.0 8. 55 1. 202 Dicresy] a-naphthyl phosphate dimer acid232. 6 10. 41 1.186 Dic-resyl p-xenyl phosphate 235.8 10. 31 1. 183Dicresyl p-xeuyl phosphate dimer acid 310. 6 13. 35 1.164 Dicresylo-xenyl phosphate 257. 6 9. 45 1.190 Dicrcsyl o-xenyl phosphate (1 acid340. O 11. 46 1. 168 Tris(2,4 dimethylphenyl) phosphate... 201.3 7.71Tris(2,4-dimethylphenyi) phosphate dimer acid 274.0 9. 32Tris(p-tert.-butyl phenyl) phosphate... 750. 4 1ris(p-tert.-butylphenyl) phosphate dimer acid 1, 008. 1 Tris(meta-isopropylphenyl)phosphate. 42.7 Tris(meta isopropylphenyl) phosphate dimer acid 56. 4Meta-isopropylphenyl diphenyl phosphate 17.7 Meta-isopropylphenyldiphenyl phosphate dimer acid 24. 5 di(o-Chl0rophenyl) phenylphosphate-33.1 di(o-Chlor0phenyl) phenyl phosphate dimer acid 44.1

It has also been found that anti-rust protection, as measured by themethod hereinbefore described, for as long as sixty days and at leastforty-five days can be obtained with the basic fluid formulations ofthis invention by incorporating therein an additive amount of an alkarylacid ester of phosphorus which can be represented by the formula:

Where R is an alkylphenyl radical and where R is hydrogen or analkylphenyl radical. By alkylphenyl radical is meant a phenyl radicalcontaining one or two like or unlike substituents, such as amyl, andtheir various isomers. It is preferred that the alkyl substituents be onthe 2 and/or 4 positions of the phenyl nucleus, and it is particularlypreferred that they contain from three to six carbon atoms.

These acid esters are prepared by reacting phosphorus pentoxide with analkyl phenol in a molar ratio of about 1:3, the reaction product beingan equi-weight mixture of the mono(alkyl-substituted phenyl) acid esterof phosphorus and the di-(alkyl-substituted phenyl) acid ester ofphosphorus, thus;

which esters are readily separable by means well known in the art.However, from the standpoint of economy, it is not necessary to separatesaid esters since the mixture so obtained can be used.

Non-limiting examples of such preferred compounds are the mixture ofmonoand di-(2,4-di-tert.-amyl phenyl) acid esters of phosphorus preparedfrom phosphorus pentoxide and 2,4-di-tert.-arnyl phenol, the mixture ofmonoand di-(2,4-di-isoamyl phenyl) acid esters of phosphorus obtainedfrom phosphorus pentoxide and 2,4- di-isoamyl phenol, the mixture ofmonoand di-(2- isoarnyl phenyl) acid esters of phosphorus obtained fromphosphorus pentoxide and Z-isoamyl phenol, the mixture of monoanddi-(2,4-di-tert.-butyl phenyl) acid esters of phosphorus obtained fromphosphorus pentoxide and 2,4-di-tert.-butyl phenol, the mixture ofmono-and di- (Z-n-hexyl phenyl) acid esters of phosphorus obtained fromphosphorus pentoxide and 2-n-hexyl phenol, the mixture of monoanddi-(4-isopropyl phenyl) acid esters of phosphorus obtained fromphosphorus pentoxide and 4-isopropyl phenol. Other mixtures of monoanddi- (alkyl-substituted phenyl) acid esters of phosphorus which areoperable in the compositions of this invention include the products ofphosphorus pentoxide and, respec tively, Z-ethyl phenol, 4-isobutylphenol, 4-isoamyl phenol, 2,4-di-tert.-butyl phenol, 2-ethylhexylphenol, 2-n octyl phenol, 2-nonyl phenol, 2-decyl phenol, and 2- dodecylphenol. It is to be understood that either the mono-(alkyl-substitutedphenyl) acid esters of phosphorus or the di-(-alkyl-substituted phenyl)acid esters of phosphorus can be employed per se, and that any mixturethereof is contemplated.

When using the above defined alkaryl acid esters of phosphorus in thecfluid formulations of this invention an additive amount, i.e. up toabout 5% by weight, is used. The addition of these acid phosphates inthe fluid compositions of this invention does not measurably alter thephysical properties of such compositions since the dimer acid contentcan be decreased somewhat, in proportion to the amount of acid ester ofphosphorous used. Preferably the total of dimer acid plus acid ester ofphosphorous should be, for anti-rust protection of the order of 45-60days, at least about 2.5%. Thus the dimer acid content can be in therange of about and the amount of acid ester of phosphorous can be in therange of about 0.1-5%.

Typical formulations containing the base stock, dimer acid and alkarylacid ester of phosphorus, which provide anti-rust protection for from 45to 60 days in the aforedescribed rust test are the following.

Component: Percent by weight Tricresyl phosphate 95.0 Dimerized linoleicacid 2.5 Diarnylphenyl acid phosphate 2.5

Tricresyl phosphate 97.0 Dimerized linoleic acid 2.7 Diamylphenyl acidphosphate 0.3

Cresyl diphenyl phosphate 97.0 Dimerized linoleic acid 2.7 Diamylphenylacid phosphate 0.3

If desired, oxidation inhibitors can also be added to the fluids of thisinvention, examples of which are alphaor beta-naphthol, N-phenylalpha-naphthylamine, pamino-diphenyl amine, N,N-diphenyl benzidine,N,N'- di-Z-naphthyl p-pheny1ene diamine, phenothiazine and the silicaanalog of phenothiazine. The amount of such inhibitors which isgenerally not more than about 1% by weight. Also, for some applications,it may be desirable to add small amounts of various other functionaladditives such as viscosity index improvers, e.g., a polyrnerizedrnethacrylate ester, an alkylated polystyrene, or the polyethercondensation products of ethylene oxide or propylene oxide, or both,with a glycol such as ethylene glycol, propylene glycol, butanediol,etc., or with an aliphatic alcohol such as butanol, octanol, decanol,tridecanol, etc., pour point depressors, detergents, other corrosionandrust-inhibiting agents, anti-Wear and lubricity agents, anti-foamingagents such as the silicone polymers, and the like.

By fluid triaryl phosphate is meant those triaryl phosphates which arefluid, i.e., mobile, at ordinary temperatures, i.e., above about 30 F.Such triaryl phosphates are known to the art, and thus need not bespecifically enumerated. Thus, for example, triphenyl phosphate wouldnot meet the above definition, as it is a solid below about 121 F., afact well known to the art, and therefore is not contemplated within thescope of this invention.

While this invention has been described with reference to variousspecific examples and embodiments, it is to be understood that theinvention is not limited thereto and that it can be variously practicedwithin the scope of the following claims.

What is claimed is:

1. A fire-resistant functional fluid composition comprising a majoramount of a fluid triaryl phosphate represented by the structure where RR and R are selected from the group consisting of phenyl, alkylphenyl,halophenyl, haloalkylphenyl, and alkylhalophenyl, in which any alkylsubstituent has up to 10 carbon atoms, from about 0.25% to about 10% byweight of a dimer acid produced by the condensation of unsaturatedaliphatic monocarboxylic acids having between about 16 and 18 carbonatoms, and from about 0.1% to about 10% by weight of an acid ester ofphosphorus represented by the structure where R is alkylphenyl having upto 12 carbon atoms in the alkyl substituent and R is selected from thegroup consisting of hydrogen and alkylphenyl having up to 12 carbonatoms in the alkyl substituent.

2. A fire-resistant functional fluid composition comprising a majoramount of a fluid triaryl phosphate represented -by the structure O=POR2 Where R R and R are alkylphenyl, having up to 10 carbon atoms in thealkyl substituents, from about 0.25% to about 10% by weight ofdilinoleic acid, and from about 0.1% to about 10% by weight of an acidester of phosphorus represented by the structure where R and R arealkylphenyl having 3 to 6 carbon atoms in the alkyl portion thereof.

3. A fire-resistant functional I'luid composition comprising a majoramount of tricresyl phosphate, from about References Cited in the fileof this patent UNITED STATES PATENTS 2,080,299 Benning et a1. May 11,1937 2,631,979 McDermott Mar. 17, 1953 FOREIGN PATENTS 205,453 AustraliaDec. 21, 1956 790,231 Great Britain Feb. 5, 1958

1. A FIRE-RESISTANT FUNCTIONAL FLUID COMPOSIT0N COMPRISING A MAJORAMOUNT OF A FLUID TRIARLYL PHOSPHATE REPRESENTED BY THE STRUCTURE